Giant panda Kelin on Monday morning gave birth to twin female cubs at a panda breeding center in Chengdu City, southwest China’s Sichuan Province.

It is the world’s first set of giant panda twins born in 2015, and both of them are in good health, according to the breeders with the Chengdu Research Base for Giant Panda Breeding.

The older sister weighs 118 grams (4.1 ounces) and the younger sister 70 grams (2.4 ounces), and both of them drink about one milliliter milk per meal, said the breeders.

Their mother Kolin was impregnated through artificial insemination in January. She gave birth to the twins after going into labor for two hours.